Polyaryl ether thickened to a grease with an aryloxy benzoate



United States Patent 3,213,025 POLYARYL ETHER THICKENED TO A GREASE WITHAN ARYLOXY BENZOATE John F. Hedenburg, Cheswick, Pa., assignor to GulfResearch & Development Company, Pittsburgh, Pa., a corporation ofDelaware No Drawing. Filed Mar. 15, 1962, Ser. No. 180,035 3 Claims.(Cl. 252-42) This invention relates to an improved lubricatingcomposition and more particularly to a polyaryl ether lubricant suitablefor high temperature lubrication.

The trend in design of modern aircraft has accentuated the need forgreases which will lubricate anti-friction bearings operating at highrotational speeds and high temperatures. While considerable progress hasbeen made in recent years in producing improved aircraft greases somedifiiculty has been encountered in producing a grease which willeffectively lubricate bearings operating at high rotational speeds andhigh temperatures for prolonged periods of time.

I have discovered that a lubricating composition having improvedlubricating characteristics for an extended period of time when used tolubricate bearings operating at an elevated temperature under highrotational speeds can be obtained by incorporating an alkali metal saltof an aryloxy benzoic acid in a polyaryl ether in an amount suflicientto produce a composition having the consistency of a grease. Thus, theimproved lubricating composition of my invention comprises a dispersionin a polyaryl ether of a sufficient amount to thicken the polyaryl etherto a grease consistency of an alkali metal salt of an aryloxy benzoicacid.

The thickening agents employed in the composition of the invention arethe alkali metal salts of aryloxy benzoic acids, which are exemplifiedas follows: sodium o-phenoxy-benzoate; sodium m-phenoxybenzoate; sodiump-phenoxybenzoate; sodium o-naphthoxybenzoate; sodiummnaphthoxybenzoate; sodium p-naphthoxybenzoate; potassiumd-phenoxybenzoate; potassium p-napthoxybenzoate; lithiumo-phenoxybenzoate; lithium p-napthoxybenzoate; etc.

The alkali metal salts of the aryloxy benzoic acids can be prepared bytreating an aryloxy benzoic acid with an aqueous alkali solution. Forexample, sodium o-phenoxybenzoate can be prepared by reacting aqueoussodium hydroxide and o-phenoxybenzoic acid in equimolar proportions atroom temperature. Neither the compounds per se nor their method ofpreparation constitutes any portion of the invention. The amount of thealkali metal salt of an aryloxy benzoic acid which I use is an amountsufficient to thicken the lubricating oil to a grease consistency. Ingeneral, this amount comprises about to about 50 percent by weight ofthe total composition. In most in stances, a composition having theconsistency of a grease can be prepared when the alkali metal salt ofthe aryloxy benzoic acid comprises about to about percent by weight ofthe total composition.

The polyaryl ether in which the alkali metal salt of the aryloxy benzoicacid is incorporated is preferably a polyphenyl ether. Exemplary of thepolyphenyl ethers are bisphenoxyphenyl ether, bis (phenoxyphenoxy)phenylether and bis(phenoxyphenoxy)benzene. The ethers can be used either inthe form of a substantially pure individual isomers or in the form ofmixtures of isomers such as mixed ortho, meta and para isomers ofbis(phenoxyphenoxy)benzene. Exemplary of exceedingly good individualisomers are m-bis(m-phenoxyphenoxy)benzene andbis-m(m-phenoxyphenoxy)phenyl ether.

If desired, a blend of polyaryl ethers having different viscosities maybe employed as the lubricant base instead of a single polyaryl ether bymeans of which a base 3,213,025 Patented Oct. 19, 1965 lubricant havinga particular viscosity may be secured. Therefore, depending upon theparticular use for which the ultimate composition is designed, thelubricant base may be a bis(phenoxyphenoxy)benzene, abis(phenoxyphenoxy)phenyl ether or a mixture thereof. The polyaryl ethercontent of the composition prepared according to this inventioncomprises about 50 to about percent by weight of the total composition.

In compounding the compositions of the present invention, various mixingand blending procedures may be used. In a preferred embodiment of theinvention, the polyaryl ether and the alkali metal salt of the aryloxybenzoic acid together with conventional lubricant additives, if desired,are mixed together at room temperature for a period of 10 to 30 minutesto form a slurry. During this initial mixing period some thickening isevidenced. Some lumps may be formed. The slurry thus formed is thensubjected, to a conventional milling operation in a ball mill, a colloidmill, homogenizer or similar device used in compounding greases to givethe desired degree of dispersion. In the illustrative composition ofthis invention, the slurry was passed twice, by means of a pump, througha Premier Colloid Mill set at a stator-rotor clearanee of 0.002 inch.Maximum thickening occurred on the second pass through the mill.

The lubricating composition of this invention can contain conventionallubricant additives, if desired, to improve other specific properties ofthe lubricant without departing from the scope of the invention. Thus,the lubricating composition can contain a filler, a corrosion and rustinhibitor, an extreme pressure agent, an antioxidant, a metaldeactivator, a dye and the like. Whether or not such additives areemployed and the amounts thereof depend to a large extent upon theseverity of the conditions to which the composition is subjected andupon the stability of the lubricating base in the first instance. Sincethe polyaryl ethers, for example, are in general more stable thanmineral oils, they require the addition of very little, if any,oxidation inhibitor. When such conventional additives are used they aregenerally added in amounts between about 0.01 and 5 percent by weightbased on the Weight of the total composition.

In order to illustrate the lubricating characteristics of a greasecomposition of the invention at 20,000 revolutions per minute and at atemperature of 400 F., Pope spindles were used in a test proceduresimilar to that outlined by the Coordinating Research Council TentativeDraft (July 1954) Research Technique for the Determination ofPerformance Characteristics of Lubricating Grease in AntifrictionBearings at Elevated Temperatures, CRC Designation L-35. According tothis procedure, 3 grams of the grease to be tested are placed in abearing assembly containing an eight-ball SAE No. 204 ball bearing. Ingeneral, bearings fabricated from high speed tool steel and ballretainers fabricated from silver-plated berylliumcopper (MRC 204S17) areused as both test and outboard bearings. The bearing assembly which ismounted on a horizontal spindle is subjected to a radial load of 5pounds. The portion of the spindle upon which the test bearing assemblyis located is encased in a thermostatically controlled oven. By thismeans the temperature of the bearing can be maintained at a desiredelevated temperature which in the test reported hereinafter was 400 F.The spindle is driven by a constant belt-tension motor drive assembly,capable of giving spindle speeds of 20,000 revolutions per minute. Thetest continues until the lubricant fails. The lubricant is considered tohave failed when any one of the following conditions occurs: (1) spindleinput power increases to a value approximately 300 percent above thesteady state condition at the test temperature; (2) an increase intemperature at the test bearing of 20 F. over the test temperature; or(3) the 3 test bearing locks or the drive belt slips at the start orduring the test.

The polyaryl ether used in preparing the lubricating compositionsummarized in Table I was mixed isomers of bis(phenoxyphenoxy)benzenehaving as typical characteristics a viscosity at 100 F. of 1691 SUS, aviscosity at 210 F. of 71 SUS and a pour point of +40 F.

The sodium o-phenoxybenzoate was prepared by new tralizing (pH of 7) atroom temperature, 100 g. of ophenoxybenzoic acid dissolved in a minimuof 95 percent ethanol with a 50 percent aqueous solution of sodiumhydroxide. Water and additional ethanol were added just to dissolve theprecipitate. The solution was then added With stirring to three litersof acetone from which the product precipitated. The product was thenWashed twice with acetone and dried. The dried product, sodium ophenoxybenzoate, melted at 345 C. (653 F.).

In preparing the lubricating composition, the polyaryl ether and thealkali metal of o-phenoxybenzoic acid were mixed at room temperature fora period of 10 to 30 minutes. The slurry thus formed was passed twicethrough a Premier Colloid Mill set at a stator-rotor clearance of 0.002inch. The thickened lubricating composition thus prepared had thefollowing approximate make-up and The long performance life of thecomposition of the invention at a high rotational speed and a hightemperature is self evident from the above data.

Other lubricating compositions within the scope of the invention areillustrated in Table II. The polyaryl ethers shown in Table II have thefollowing typical characteristics.

Viscosit SUS:

At iii) F 1, 567 1,691 3, 565 At 210 F 70 71 118 Pour Point, F +35 +40+70 (1) m-Bis(m-phenoxyphenoxy)benzene.

(2) Bis(phenoxypheuoxy)benzene (mixed isomers),

(3) Bis-111(m-phenoxyphenoxy)phenyl ether,

4 Table II Composition, percent By Weight B C Polyaryl Ether:

m-Bis(rn-phenoxyphenoxy)benzene". Bis(phenoxyphe110xy)benzene (mixedisomers) Bis-m(m-phenoxyphenoxy)phenyl ether Thiekener:

Soium o-uaphthoxybenzoate Potassium p-naphthoxybenzoate Lithiump-phenoxybenzoate While my invention has been described with referenceto various specific examples and embodiments, it will be understood thatthe invention is not limited to such examples and embodiments and may bevariously practiced within the scope of the claims hereinafter made.

I claim:

1. A lubricating composition capable of functioning in bearings rotatingat speeds up to about 20,000 r.p.m. at temperatures up to about 400 F.consisting essentially of 5 a dispersion in a major amount of apolyphenyl ether of a References Cited by the Examiner UNITED STATESPATENTS 2,623,854 12/52 Morway et al 25241 2,690,429 9/54 Morway et a125242 3,012,966 12/61 Copes et a1. 447 3,113,849 12/63 McCoy 447 OTHERREFERENCES Synthetic Lubricants, by Gunderson et al., Reinhold Pub.Corp., New York, 1962, page 460.

DANIEL E. WYMAN, Primary Examiner.

JULIUS GREENWALD, Examiner.

1. A LUBRICATING COMPOSITION CAPABLE OF FUNCTIONING IN BEARINGS ROTATINGAT SPEEDS UP TO ABOUT 20,000 R.P.M. AT TEMPERATURES UP TO ABOUT 400*F.CONSISTING ESSENTIALLY OF A DISPERSION IN A MAJOR AMOUNT OF A POLYPHENYLETHER OF A SUFFICIENT AMOUNT TO THICKEN THE POLYPHENYL ETHER TO A GREASECONSISTENCY OF SODIUM O-PHENOXYBENZOATE.